An arrangement in which, when molding a resin molded article, a mold core on the side opposite to a design surface is separated from a resin surface so as to form a gap, thus reducing heat transference between the resin surface and the mold core and thereby preferentially causing a sink mark in a portion that faces the gap, and as a result suppressing a sink mark on the design surface, is already known from Patent Publication 1.    Patent Publication 1: Japanese Patent No. 3512595